An integrated, multidisciplinary research program is in progress which has as a general goal the identification and control of acute, intercurrent processes which may influence growth and development of the respiratory system with resultant long-term sequelae. Longitudinal studies of infants and children are establishing normal patterns of growth of lung function and the impact on this of acute respiratory infection with emphasis on the syndrome of bronchiolitis. This prospective clinical study is complemented by retrospective approaches of two types: 1) comprehensive evaluations of patients referred for recurrent or chronic progressive pulmonary diseases (including those with cystic fibrosis, sarcoidosis and anti-protease or immune deficiencies) to identify responsible defects in pulmonary defense mechanisms; and 2) follow-up studies of children in the community documented to have had infections during the past decade with agents such as respiratory syncytial virus. Relevant basic laboratory studies are being performed using experimental models of respiratory diseases (animals) and cultures of specialized pulmonary cells infected with respresentative agents to define the mechanisms of injury, repair and protection. This combination of clinical and basic research should lead to improved means of diagnosis, therapy and prevention of respiratory diseases and their complications or sequelae.